No circular dependencies

Circular dependencies cause modules to receive undefined at initialization time because JavaScript resolves the cycle by partially evaluating one module before the other is ready. This produces runtime bugs that are invisible to the type system and nearly impossible to reproduce reliably. CWE-1120 (Excessive Complexity) applies: circular graphs make the build tool's evaluation order non-deterministic and prevent tree-shaking, silently bloating your bundle. AI-generated codebases are especially prone to cycles because utility files get written to "reach back up" into components they originally served.

Find all cycles first, then break them by moving shared logic to a file that neither participant imports. Run:

npx madge --circular src/
# or
npx dpdm --circular src/

To break a cycle: extract the shared code into a new neutral module, or use dependency injection. Prevent future cycles by adding eslint-plugin-import with the import/no-cycle rule — it fails the lint check the moment a cycle is introduced.